Several studies have analyzed or summarized chemical migration from different types of food contact materials and articles (FCMs and FCAs), including plastics, paper, can coating, and reusable FCAs.
Plastics
In an article published on April 5, 2022, in the journal Food Additives & Contaminants: Part A, Carlos Wen-Li Zhou from Changsha University of Science and Technology, China, and co-authors applied a newly developed microextraction technique to assess the migration of fluorescent whitening agents from plastic FCAs. Fluorescent whitening agents are added to plastics such as polyesters and chemical fibers to brighten them. The researchers describe that they may cause allergic reactions and may have potential carcinogenic risks.
They developed an improved hollow fiber liquid-phase microextraction method coupled with ultra-high performance liquid chromatography-mass spectrometry (HPLC-MS) to determine trace levels of migrating analytes. This type of microextraction method has been used for the extraction and pre-concentration of trace organic compounds from foods before. After having established the method for their purpose, the researchers used it to study the migration of five whitening agents from four types of disposable plastic containers. Migration experiments were conducted according to the national standard in Great Britain BR 31604.1–2015 at 100 °C for 1 h into three types of food simulants. Four out of the five brighteners were found to migrate in levels between 0.020 mg/kg food and 0.494 mg/kg food. “Brighteners were more prone to migrate when in contact with acid and alcoholic foods.”
Paper
In contrast to Zhou et al. who performed targeted analysis, Yelena Sapozhnikova and Alberto Nuñez from Eastern Regional Research Center, Wyndmoor, PA, USA, performed non-targeted analysis and assessed migrants from paper-based food contact materials (FCMs). Their research article was published on June 11, 2022, in the Journal of Chromatography A. They purchased 27 paper food packaging samples from supermarkets and pizzerias around Philadelphia, US, including egg containers, butcher papers, pizza boxes, and pizza box liners. After cutting the samples into pieces they conducted migration tests using food simulant at 20°C over 10 days and collected samples according to the US Food and Drug Administration (FDA) guidance for food contact substances. Migrated chemicals were analyzed with LC- high-resolution MS and identified by comparing spectra and/or the structure with the Extractable and Leachable high-resolution accurate mass (HRAM) database, MzCloud, and ChemSpider. To reduce false positives, the scientists further used orthogonal LC retention information to refine the data.
After refining the data, Sapozhnikova and Nuñez reported on 129 and 113 compounds detected in electrospray positive and negative ionization mode, respectively. Of these, they identified and characterized 153 chemicals. Over 90% of the chemicals were identified by ChemSpider and the majority by more than one of the three sources consulted. “Most of the identified migrants (47%) were intentionally added substances (IAS) and common extractable and leachable chemicals, representing chemicals added to the coating, surfactants, lubricants, and other IAS.” They further reported that only 3% of the identified chemicals were non-intentionally added substances (NIAS).
Among the identified chemicals were bisphenol A (BPA, CAS 80-05-7) and diethylene glycol n-butyl ether (CAS 112-34-5), which are listed in the Food Packaging Forum’s Food Contact Chemicals Database (FCCdb) as endocrine-disrupting chemicals (EDCs). Besides BPA, the researchers also identified bisphenol S (BPS, CAS 80-09-1) and confirmed their identification with analytical standards. Quantifying the concentrations showed that they ranged from 0.1-0.3 µg/kg (BPA) and 0.8-4.8 µg/kg (BPS), which is currently “below the established regulatory limits for migration” in the EU. However, in December 2021, the European Food Safety Authority (EFSA) proposed to lower the tolerable daily intake (TDI) of BPA from 4 µg/kg body weight/day to 0.04 ng/kg body weight/day (FPF reported) and in May this year also the US FDA agreed to review the safety of BPA for use in food packaging (FPF reported).
Michaela Lerch and co-authors from the Technical University of Denmark, Lyngby, Denmark, also assessed chemical migration from paper FCMs but selected items that were treated with per- and polyfluorinated alkyl substances (PFAS). In their research, published on May 30, 2022, in the journal Food Chemistry, they were interested in migration of PFAS when FCAs are subjected to high temperatures. PFAS are widely used in paper and cardboard to provide the packaging with resistance to water, oil, and other fats and have been associated with several adverse health effects (FPF reported and here).
Lerch and co-authors purchased three microwavable disposable plates and three muffin cups, all based on paper and known to contain PFAS, on the Scandinavian market between 2017 and 2019. They performed migration experiments into food simulants (20 and 50% ethanol) according to the Plastics Regulation (10/2011) with some adjustments, since no specific regulation is existing for paper FCMs. They compared it with migration into food, i.e., oatmeal porridge and tomato soup for the plates and muffins for the muffin cups, to investigate the suitability of the “plastic migration test conditions” for paper. The migration of three PFAS classes, perfluorinated carboxylic acids/sulfonic acids (PFCAs/PFSAs), polyfluoroalkyl phosphate esters (PAPs), and fluorotelomer alcohols (FTOHs), was measured using LC-MS/MS.
The scientists reported migration of PFCAs and FTOHs in all food samples under the high-temperature conditions applied. Comparison with real food showed that FTOHs “did not migrate into 20% ethanol” while “migration of PFCAs and FTOHs to 50% ethanol was significantly higher than migration to real food.” This made the authors conclude that the use of food simulants may lead to over- or underestimation of PFAS migration and “should be approached with caution, especially for the analysis of FTOHs in food with lipophilic character.”
Lerch et al. also assessed the risk from migrated PFAS by comparing calculated dietary exposures with the European Food Safety Authority’s (EFSA) safety guidelines. This showed that dietary exposure for children exceeded the safety threshold of 0.63 ng/kg body weight/day by up to nine times. Therefore, the authors answered their research question of “Is the use of paper FCMs treated with PFAS safe for high-temperature applications?” with “no”.
According to a review published in 2021, PFAS are still widely-used in FCMs such as baking paper and fast-food wrappers (FPF reported). In the US, states are developing local PFAS regulations with some states banning intentionally added PFAS in paper packaging (FPF reported and here) and five European nations are drafting a dossier to restrict PFAS in the EU entirely (FPF reported).
Reusables
In an article published on June 13, 2022, in the journal Food Packaging and Shelf Life, Antía Lestido-Cardama from the University of Santiago de Compostela, Spain, and co-authors analyzed brominated flame retardants (BFRs) in black repeat-use FCAs. The authors bought 21 FCAs in retailers in Santiago de Compostela, Spain, which they used to develop or refine and evaluate three analytical techniques for BFR identification, including direct analysis in real-time (DART) ionization coupled to HRMS, X-ray fluorescence (XRF), and high-pressure LC-MS/MS. Subsequently, they applied the techniques to study migration of tribromophenol (TBP, CAS 118-79-6), tetrabromobisphenol-A (TBBPA, CAS 79-94-7), and decabromodiphenyl ether (BDE-209, CAS 1163-19-5) from a bottle stopper, a spice mill, a coffee maker and an isothermic drinking beaker into food (pepper) or food simulants (20 and 95% ethanol) under repeated-conditions.
The scientists detected BFRs in three of the FCAs in levels of up to 90 µg/kg in 95% ethanol. Depending on the analyte and the FCA, migrating chemical concentrations either increased or decreased with repeated migration. Since none of the analyzed BFRs are listed on the positive list of chemicals in the regulation for plastic FCMs (EC 10/2011), the authors emphasized that “these FCAs are likely violative” and that “the quality of recycled materials in the manufacture of food contact materials should be monitored.” Also, previously high levels of BFR have been reported in recycled plastics (FPF reported) or materials intended for recycling (FPF reported).
Can coatings
In a review article published on April 20, 2022, in the journal Comprehensive Review, Antía Lestido-Cardama from the University of Santiago de Compostela, Spain, and co-authors summarized different aspects of coatings used for food and beverage cans, including evidence on chemical migration. They provide an overview of the different types of can coatings, which use different chemistries. Furthermore, they evaluate the analytical methods for the identification of migrating compounds and discuss the chemicals themselves, dietary exposure, and regulatory aspects.
Since epoxy resins based on bisphenol A diglycidyl ether (BADGE, CAS 1675-54-3) have been criticized due to the endocrine-disrupting properties of BPA, other coatings such as polyesters and acrylic are being developed and used (FPF reported).
Lestido-Cardama and co-authors also summarized which methods are used after migration. Accordingly, samples are usually pretreated by a combination of solvent extraction (most commonly SPE) and clean-up (QuEChERS) before separation. Detection is usually performed by liquid or gas chromatography coupled to mass spectrometry. The authors further summarized that “canned food can be an important source of exposure to different chemicals, including bisphenols and BADGE” (FPF reported and here). For these compounds, low dietary exposures have been reported in the literature. However, some of the derivates were found to exceed specific migration limits existing in Europe.
The authors highlighted that most of the reviewed studies have analyzed the migration of starting substances, such as monomers, while oligomers and NIAS have been largely neglected. Besides these, they emphasized that also exposure to chemical mixtures needs to receive more attention in future studies. From a regulatory perspective, in the EU varnishes and coatings fall under the Framework Regulation No 1935/2004 which applies to all FCMs. Several EU Member States have specific regulations but they are not harmonized. However, to support safety, “it would be of value to have a harmonized European legislation for varnishes and coatings,” the authors concluded.
References
Lerch, M. et al (2022). “Is the use of paper food contact materials treated with per- and polyfluorinated alkyl substances safe for high-temperature applications? – Migration study in real food and food simulants.” Food Chemistry. DOI: 10.1016/j.foodchem.2022.133375
Lestido-Cardama, A. et al (2022). “Food and beverage can coatings: A review on chemical analysis, migration, and risk assessment.” Comprehensive Review. DOI: 10.1111/1541-4337.12976
Lestido-Cardama, A. et al (2022). “Determination of BFRs in food contact articles: An analytical approach using DART-HRMS, XFR and HPLC-MS/MS.” Food Packaging and Shelf Life. DOI: 10.1016/j.fpsl.2022.100883
Sapozhnikova, Y. and Nuñez, A. (2022). “Non-targeted analysis with liquid chromatography – high resolution mass spectrometry for the identification of food packaging migrants.” Journal of Chromatography A. DOI: 10.1016/j.chroma.2022.463215
Zhou, W.-L. et al (2022). “Application of an improved hollow fiber liquid phase microextraction technique coupled to LC-MS/MS to studying migration of fluorescent whitening agents from plastic food contact materials.” Food Additives & Contaminants: Part A. DOI: 10.1080/19440049.2022.2066192
